Friction-induced Vibration Research Articles

Transition of synchronization state during the quasiperiodic route to chaos in coupled friction-induced continuous oscillators

Friction-induced vibration, particularly associated with the squealing problem in disk brake systems, has been a longstanding challenge in the automotive industry. In our research, we employed the synchronization theory to gain insights into the interaction between two coupled cantilever beams attached with tip masses. This proposed model emulates the dynamics of a mountain bike disk brake assembly. The work explores a range of collective behaviors, including synchronized periodic, multi-periodic, quasiperiodic, as well as desynchronized chaotic and quasiperiodic oscillations. Despite numerous studies reported on the synchronization phenomenon in discrete friction-induced oscillatory systems, there appears to be a lack of similar research on continuous systems. This work stands as the first of its kind in exploring the dynamics of synchronization between two coupled continuous systems exhibiting a quasiperiodic route to chaos. A bifurcation study is conducted utilizing the Poincaré points corresponding to the local maxima of oscillation amplitude with respect to the zero-velocity crossing. The results showed the existence of narrow multi-periodic windows during the quasiperiodic route at several locations. Additionally, the existence of multiple quasiperiodic attractors exhibiting different states of synchronization for the same set of parameters is observed. We analyzed the time evolution of the cumulative instantaneous phase difference between the coupled signals and identified distinct states of synchronization possessed by the system. The coupled system undergoes interesting phenomena such as complete phase lock, intermittent phase lock, and phase drifting. Moreover, the transition occurring to the state of synchronization during the quasiperiodic route to chaos is studied employing the phase locking value, the Pearson linear correlation coefficient, and the relative mean frequency. Notably, our findings revealed that while the Pearson correlation can effectively identify both the mode and strength of synchronization, other measures such as phase lock value and relative mean frequency only reflect synchronization strength.

The influence of disks deformation on the stability analysis of an aircraft braking system

Friction-induced vibration emanating from aircraft braking system is a key issue in the design phase, due to the significant damage it can cause to the brake structure. Although the problem of unstable vibrations in aircraft braking systems has been studied by a number of researchers, the suitability of the mechanical modeling strategy for predicting instabilities remains an open problem. The need for relevant numerical models is therefore essential in order to be as predictive as possible during the design phase. Preliminary studies must therefore be carried out to validate or invalidate the modeling hypotheses traditionally used. Indeed the stability analysis of an aircraft braking system is performed in order to study a low-frequency instability. An industrial model is used, hence reducing the number of degrees of freedom (DoF) is of utmost importance in order to have reasonable computation times. When studying low-frequency phenomena, this can be achieved by neglecting the deformations of the disks. However, no current study has shown that this hypothesis is realistic. So the aim of this paper is to assess the effect of the rigidity hypothesis on the results predicted by the stability analysis. In order to do so, the stability analysis results of a model with rigid disks and one with non-rigid disks are compared, with a particular attention on the main instability phenomenon. It is found that considering rigid disks has a very limited influence on the frequency of the low-frequency eigenmodes, but it over-predicts the real part of the unstable eigenmode. Besides, a component mode synthesis (CMS) technique is shown to reduce significantly the size of the non-rigid disks model while ensuring a satisfying precision regarding eigenmodes prediction.

Effects of periodic structures on friction-induced vibrations in catenary-pantograph systems

Friction-induced vibration in catenary-pantograph systems is a well-known instability phenomenon that has not been sufficiently investigated. This instability accelerates the wear of contact wires and requires a train driver to confirm safety, which leads to train delays. Therefore, it is important to elucidate the instability mechanisms and establish countermeasures. To address this issue, we conducted experiments using a real pantograph and a test facility that can simulate sliding conditions by rotating a rigid disk. These experiments characterized the instability reported in actual rail operations. Furthermore, numerical investigations found that the experimental results could be explained by assuming Coulomb friction for an experimentally validated pantograph model. However, this previous study did not examine the effects of the periodic catenary structures or propose countermeasures for their instability contribution. In this study, experiments and simulations based on actual equipment were conducted to investigate the effects of periodic structures. The simulations integrated a finite element method-based catenary model with a flexible multibody dynamics-based pantograph model. The experimental and numerical investigations clarified that the instability is caused by the asymmetry of the stiffness matrix due to Coulomb friction, and that standing waves formed in the contact wires between hangers significantly affect stability. Furthermore, the results suggested that these waves could be the basis of countermeasures for preventing instability. These results can contribute to the design of catenaries and pantographs with improved stability.

Computer Vision-Based Research on the Mechanism of Stick–Slip Vibration Suppression and Wear Reduction in Water-Lubricated Rubber Bearing by Surface Texture

Water-lubricated rubber bearings are a critical component of the propulsion systems in underwater vehicles. Particularly under conditions of low speed and high load, friction-induced vibration and wear often occur. Surface texturing technology has been proven to improve lubrication performance and reduce friction and wear; however, research on how different texture parameters affect friction-induced vibration and wear mechanisms remains insufficient. In this study, various texture patterns with different area ratios and aspect ratios were designed on the surface of water-lubricated rubber bearings. By combining these designs with an in situ observation system based on computer vision technology, the effects of texture parameters on bearing friction, vibration, and wear were thoroughly investigated. The experimental results show that surface textures play a critical role in improving hydrodynamic effects and stabilizing the lubrication film at the friction interface. Specifically, textures with a high area ratio (15%) and aspect ratio (3:1) exhibited the best vibration suppression effect, primarily due to the reduction in actual contact area. However, excessively high area ratios may lead to increased surface wear. This study concludes that a reasonable selection of texture area and aspect ratios can significantly reduce frictional force fluctuations and vibration amplitude, minimize surface wear, and extend bearing life.

Effect of Molybdenum Bisulfide (MoS2) Particle Size on Tribological and Vibration Reduction Properties of Thermoplastic Polyurethane

The incorporation of lubricating filler can improve the self-lubricating properties of polymers and mitigate friction-induced vibration under harsh conditions. However, filler performances significantly vary depending on its size. In this study, molybdenum bisulfide (MoS2) particles of various sizes were utilized as lubricating additives to reinforce thermoplastic polyurethane (TPU). The results showed that an appropriate decrease in the particle size of MoS2 facilitated more efficient stress transfer from the polymer to the particle due to strengthened interfacial interaction, resulting in improved mechanical properties of the reinforced TPU composites. Additionally, the adsorption property of the MoS2 particle improved, extending the duration of the MoS2 tribofilm. These beneficial phenomena endow TPU composites with excellent tribological and frictional vibration reduction properties, with the 500 nm MoS2 presenting the best reinforcing effect. However, further reduction in particle size caused particle agglomeration, which adversely affected the mechanical and self-lubricating properties of the composite and eventually reduced the frictional vibration reduction properties. The findings obtained herein provide a valuable reference for developing a novel polymer with excellent friction and vibration reduction properties.

Enhancing Water Lubrication in UHMWPE Using Mesoporous Polydopamine Nanoparticles: A Strategy to Mitigate Frictional Vibration.

Establishing a persistent lubrication mechanism and a durable tribo-film on contact surfaces is identified as crucial for improving the tribology and vibration characteristics of polymer materials under water-lubricated conditions. This study focuses on enhancing tribological performance and reducing frictional vibrations in ultrahigh molecular weight polyethylene (UHMWPE) through the incorporation of mesoporous polydopamine (MPDA) nanoparticles. In the experiments, MPDA nanoparticles were synthesized and blended with UHMWPE to create UHMWPE/MPDA composites. The interactions between these composites and zirconia (ZrO2) ceramic balls under water lubrication were examined. The results show that when the MPDA content of the composite is 1.5 wt %, the coefficient of friction and wear rate are reduced by 40% and 52% compared with those of pure UHMWPE, respectively. This notable enhancement helped to mitigate friction-induced vibrations, particularly those caused by intermittent sticking and slipping motions. MPDA nanoparticles were shown to act as reservoirs for water, releasing and replenishing water based on the loading conditions, which sustained continuous water-based lubrication at the composite surfaces. Additionally, the surface deformation behavior of the composite material is significantly weakened, which provides a more stable friction surface. This work introduces a novel approach to enhance the interface stability of polymers in water-lubricated environments, offering guidance for developing advanced materials and reducing friction and wear in engineering applications.

Using lubricant composition to control friction-induced-vibration in an elastomer-steel contact representing a hydraulic seal

Hydraulic seals are key industrial components that can suffer from unwanted friction induced vibration (FIV). The types of FIV mechanism that occur in these components, and how they may be controlled, are not well known. We conducted sliding friction tests on contacts between seal materials, lubricated by hydraulic fluids, under speeds and contact pressures typical of hydraulic machines. FIV that occurred under certain conditions was captured and analysed. Results suggest 1) two FIV mechanisms are occurring: classic stick-slip and speed dependant friction instability, the 2) occurrence and severity of these mechanisms are correlated with the ratio of static to dynamic friction and the gradient of the friction vs. speed (Stribeck) curve, respectively, 3) these parameters can be controlled by including an appropriate additive package in the lubricant and this significantly reduces FIV, 4) most FIV occurs at low temperature and high load since these both lead to low kinetic friction (due to thicker hydrodynamic films and smoother surfaces) and thus promote stick-slip. This may explain instances of noise known in practice as the “Monday-morning effect” and suggests how this too may be alleviated through lubricant formulation.

A method to enhance the performance of elastic damping component to improve tribological behavior at the high-speed train braking interface: Deformation optimization through perforation structure

The deformation capability of elastic damping component (EDC) significantly influences the tribological behavior at high-speed train braking interfaces. The key prerequisite to fully exploit its efficacy lies in ensuring that the EDC exhibits appropriate deformation. In this work, we propose aperture processing in different regions of the EDC to optimize its deformation area and improve the interfaces tribological behavior. The EDC was mounted on the rear side of the friction block, and experiments on friction braking were carried out using a custom-built simulation rig designed to test the braking performance. This enables the study of the friction and wear characteristics across different EDC conditions, along with the characteristics related to friction-induced vibration and noise (FIVN). A finite element model (FEM) was developed reflecting the primary structure of the test rig, with initial surface wear simulations conducted on the blocks to achieve wear surfaces approximating the experimental outcomes. Implicit dynamic analysis (IDA) was then conducted based on this foundation. The enhancement in tribological behavior through optimizing the EDC deformation area was analyzed by integrating test results with finite element analysis (FEA) findings. The results indicate that aperture processing in different regions of the EDC has no significant effect on its dynamic response but can significantly alter its deformation characteristics, thereby achieving optimization of the EDC deformation. Adjusting apertures in various sections of the EDC markedly affects the development pattern and strength of FIVN. However, this approach maintains the fundamental characteristics of the braking system. Aperture processing enabling more extensive deformation in the EDC can notably interrupt FIVN continuity, showing clear intermittent characteristics, while potentially increasing FIVN intensity. The EDC mainly affects the tribological behavior by influencing contact characteristics such as the oscillation intensity of contact area and frictional force, thereby altering the characteristics of FIVN. The overall deformation of the EDC has a considerable effect on the movement of braking interface debris, as well as wear patterns, eccentric wear, and contact plateaus characteristics. An improperly designed deformation area in the EDC can lead to excessive softness, challenging the block's ability to maintain consistent contact with the brake disc. This issue often causes pronounced eccentric wear on the block and considerable material detachment at the wear site, which triggers intense FIVN.

The Effect of Friction Radius Variation on the Friction-Induced Vibration and Noise

The Effect of Friction Radius Variation on the Friction-Induced Vibration and Noise

Non-smooth self-excited vibration of a novel dynamical model for a disc brake

This paper proposes a new dynamic model for the study of friction-induced self-excited vibration of a disc brake system, where the pad’s motions in both radial and circumferential/tangential directions are included, which is in stark contrast to the previous studies that normally consider the pad’s motion in the tangential/circumferential direction only. The non-smooth dynamics of the system including three different states of motion, i.e., stick, slip and separation, is investigated. Both the linear stability analysis and the transient dynamic analysis are performed. The numerical results in the linear stability analysis indicate that the inclusion of pad’s radial motion in the present brake model significantly expands the ranges of operating parameters for dynamic instability than the brake model with only circumferential/tangential motion for the pad. For the transient dynamic analysis, two different methods, i.e., the time integration method and the shooting method, are employed for the calculation of steady-state response. The accuracy and efficiency of the shooting method are subsequently examined. The numerical results show rich bifurcation behaviours of the steady-state response in the present brake model with the variations of brake pressure and disc speed , and (the stiffness of the inclined spring in the radial direction) is a key parameter for controlling the occurrence of chaotic vibration in the system. Conflict of Interest Statement The authors declare no conflicts of interest.

Experimental investigation of stick-slip behaviors in dry sliding friction

Friction-induced vibration, particularly the bothersome stick-slip behavior, is a significant contributor to machine damage and component failure. In this study, the vibrational displacement, sound pressure, and coefficient of friction (COF) of several metal or alloy samples in dry conditions are tested using a reciprocating friction force test apparatus. It is found that the stick-slip behavior is more likely to occur at low sliding speeds and high normal loads. Furthermore, under the same working conditions, increasing the surface roughness of the sample or enhancing the hardness difference between the sample and the counterpart can mitigate the stick-slip behavior during the friction process. By analyzing the characteristic parameters of the stick-slip behavior, it is found that the temporal period and the stick-time decrease significantly with an increase in relative sliding speed. Additionally, the amplitude and intensity of the friction-induced noise increases with the increase of the relative sliding speed and normal load. The frequencies of the sound pressure are primarily concentrated around the natural frequency of the frictional system. Finally, we extract the COF and find that the average COF as well as the maximum and minimum COF first decreases sharply, and then becomes stable with the increase of the relative sliding speed due to the transition of friction state from stick-slip behavior to smooth sliding.

Effect of friction block thickness on the high-temperature tribological behavior of the braking interface of high-speed train

Tests on a high-speed train braking platform with friction blocks of different thicknesses revealed data on friction heat, wear, and friction-induced vibration and noise (FIVN). A finite element model (FEM) was developed using a finite element software, and then a thermal-mechanical-wear coupling simulation method was proposed to simulate the high-temperature wear of friction blocks. The results show that thicker friction blocks led to higher temperatures, eccentric wear, and increased wear debris, forming a stiff third body layer causing high-intensity FIVN. Thinner blocks showed better tribological properties and reduced FIVN. Although block thickness affects FIVN, the main frequency differences are minor. Therefore, friction block thickness should be considered as an important factor in brake pad design to manage high-temperature tribological behavior.

Biometric-Tuned E-Skin Sensor with Real Fingerprints Provides Insights on Tactile Perception: Rosa Parks Had Better Surface Vibrational Sensation than Richard Nixon.

The dense mechanoreceptors in human fingertips enable texture discrimination. Recent advances in flexible electronics have created tactile sensors that effectively replicate slowly adapting (SA) and rapidly adapting (RA) mechanoreceptors. However, the influence of dermatoglyphic structures on tactile signal transmission, such as the effect of fingerprint ridge filtering on friction-induced vibration frequencies, remains unexplored. A novel multi-layer flexible sensor with an artificially synthesized skin surface capable of replicating arbitrary fingerprints is developed. This sensor simultaneously detects pressure (SA response) and vibration (RA response), enabling texture recognition. Fingerprint ridge patterns from notable historical figures - Rosa Parks, Richard Nixon, Martin Luther King Jr., and Ronald Reagan - are fabricated on the sensor surface. Vibration frequency responses to assorted fabric textures are measured and compared between fingerprint replicas. Results demonstrate that fingerprint topography substantially impacts skin-surface vibrational transmission. Specifically, Parks' fingerprint structure conveyed higher frequencies more clearly than those of Nixon, King, or Reagan. This work suggests individual fingerprint ridge morphological variation influences tactile perception and can confer adaptive advantages for fine texture discrimination. The flexible bioinspired sensor provides new insights into human vibrotactile processing by modeling fingerprint-filtered mechanical signals at the finger-object interface.

On Dynamic Analysis and Prevention of Transmission Squawk in Wet Clutches

Abstract The genesis of clutch noise, encompassing squeaks, chatter, shudders, or judders, predominantly arises from friction-induced vibrations. As time progresses, the degradation of the clutch friction lining manifests due to diverse factors, such as the smearing of surface irregularities, elevated transmission fluid temperatures, fluctuating axial pressure, or aggressive shifting. Consequently, the slope of the friction curves tends to assume a negative gradient, giving rise to adverse damping effects like self-excited oscillations or stick-slip oscillations within the clutch pack. A lesser-discussed phenomenon, known as Squawking, occurs through analogous mechanisms discussed in this article. This article delves into investigating the occurrence of squawking noise observed in automatic transmission multi-disc clutches during low-speed up-shifts. The study discerns friction-induced vibrations as the primary contributor to squawk during the inertia phase of the clutch engagement cycle, a facet previously unidentified. During this phase, high-frequency weakly damped oscillating modes become self-excited due to the negative slope of the coefficient of friction versus slip speed curve. The coefficient of friction functions as negative damping during the inertia phase, where the energy dissipation from damping is insufficient to completely halt the oscillations, allowing them to persist at the natural frequency until clutch lock-up. Experimental data validates the proposed model and hypothesis, with results closely aligning with numerical simulations. The paper concludes by offering practical suggestions to prevent and mitigate squawk in automatic transmission wet clutches, with the aim of enhancing overall performance and reducing undesirable noise.

Energy generation from friction-induced vibration of a piezoelectric beam

The primary challenge in harnessing vibration energy with piezoelectric materials is the discrepancy in frequency between the energy source and the energy generator, which lowers the efficiency of energy harvesting. To address the challenge, a piezoelectric beam under friction-induced vibration (FIV) is designed, modeled, and studied for the first time to realize the pronounced FIV contributing to energy generation by adapting the vibrations of the continuum structure to align close to its resonant frequencies. The Stribeck friction model is applied to characterize the variation of friction based on the relative sliding velocity vr between contacting objects. The analytical solution is derived to solve the dynamic responses, and transient charging simulation validated by the experiment is utilized to assess energy output. Furthermore, parameter studies are conducted based on the validated model with regard to the material properties of the beam and piezoelectric material, electrode connections of piezoelectric patches, and friction model parameters to investigate their influences on energy output. Considering the same dimensional properties, materials with low Young's modulus E and density ρ are desired for the host structure to facilitate large dynamic strain in piezoelectric materials. With an exponential decay factor C = 8, representing optimal material contact interface, pronounced higher FIV mode can be induced leading to higher output power. A root mean square charging power PeRMS of 42.4 mW and a peak instant charging power Pe − peak of 263 mW can be achieved. In the current study, the model is implemented on a beam coupled with one piezoelectric patch, which has potential applicability to non-uniform beams with various layouts of piezoelectric patches. The presented model enables efficient optimization of continuum structural design for higher piezoelectric energy generation under friction.

The Effects of Friction Block Shape on Friction-Induced Wear, Vibration, and Noise of Train Brake Interface at Low Temperature

The Effects of Friction Block Shape on Friction-Induced Wear, Vibration, and Noise of Train Brake Interface at Low Temperature

The effect of interfacial wear debris on the friction-induced stick-slip vibration

To address the influence of wear debris on friction-induced stick-slip vibration (FISSV), a method involving grooving the friction disc was proposed. FISSV simulation experiments were conducted using a test setup. A finite element model (FEM) was established for dynamic simulations. The results show that wear debris significantly influences FISSV. Debris involved in friction will result in significant abrasive wear. Extensive debris entering the interface causes the worn surface to have numerous small contact plateaus with lower contact stiffness, leading to pronounced FISSV. Conversely, the presence of larger contact plateaus on the worn surface increases contact stiffness, making the friction system less prone to generating FISSV. Filling groove with graphite effectively suppresses FISSV. Controlling debris flow is crucial for suppressing FISSV.

DESIGN AND EVALUATION OF PIEZOELECTRIC-BASED PASSIVE DAMPING FOR HIGH FREQUENCY NOISE SUPPRESSION

This study focuses on developing a piezoelectric-based passive damper to mitigate high- frequency brake noise. The research investigates different designs of piezoelectric transducer elements to convert mechanical energy into electrical energy using a mass sliding belt test system that simulates real disc brake noise mechanisms. Integration of these electrical elements into the existing mass-sliding belt system is investigated. Five distinct piezoelectric transducer designs (Design-1, Design-2, Design-3, Design-4 and Design-5), each with unique technical specifications, boundary conditions, and scaling, are developed to suppress high frequency noise from friction-induced vibrations. To facilitate effective selection, a scoring method is employed, identifying Design-5 with a cylindrical model as the most efficient transducer design. Evaluation criteria include energy generation, compressive strength, operating temperature, weight, ergonomic usability, cost, and safety. Analyses are performed to assess potential stress-induced damage to the piezoelectric material resulting from the selected design. This study aims to contribute a novel perspective to noise reduction techniques and successfully demonstrates the integration of a piezoelectric transducer and an RLC circuit into a functional system.

Mechanism and suppression of friction-induced vibration in catenary-pantograph system

An unexplained instability phenomenon in railways is known to be caused by sliding friction in a catenary-pantograph system at low speeds. This is an important engineering problem because this instability phenomenon contributes to increased wear of contact wires and requires a train driver to confirm safety, which leads to train delays. Tribological analyses have found an increase in the friction coefficient at low speeds. Pantograph models based on the finite element method, multibody dynamics, and pin-disk model have been proposed for kinematic analyses. However, the mechanism is still uncertain, and no experimental investigations have been conducted. In this study, experimental and numerical investigations are conducted on the instability phenomenon caused by sliding friction. A method for estimating the friction coefficient for an actual pantograph is proposed and applied to experimentally investigate the instability phenomenon. A dynamic model is constructed based on various experiments. The frequency and the stable-unstable boundary of the instability phenomenon obtained in the simulations agree with those obtained in the experiment. From the dynamic model, it is found that the instability is a flutter-type instability caused by the asymmetry of the stiffness matrix due to Coulomb friction. Countermeasures for preventing the instability phenomenon based on the determined mechanism are proposed, and their effectiveness is verified by simulations and experiments. The results could contribute to the design of new pantographs to improve stability and the development of countermeasures for existing pantographs that experience instability.

Properties of Laser-Alloyed Stainless Steel Coatings on the Surface of Gray Cast Iron Discs

The influence of laser-alloyed stainless steel coatings on the properties of the surfaces of cast iron discs, such as friction-induced vibration and noise, friction coefficient, residual stress, hardness, and corrosion resistance, was investigated in this study. The experimental results show that after laser alloying, the surface hardness of the cast iron discs increased significantly. The residual stresses on the surfaces of the laser-alloyed discs changed from tensile to compressive residual stresses, while any compressive residual stresses increased by more than six times. Most of the laser-alloyed discs demonstrated better performance in friction-induced vibration and noise damping and friction reduction. Metallographic observation and XRD (X-ray diffraction) analysis results show that the laser-alloyed layer is mainly a mixture of acicular martensite and dendritic material, while the phase composition of laser-treated discs is mainly martensitic, [Fe, Ni], Fe3Si, Cr23C6, and austenite, which plays a significant role in the improvement of the properties of the laser-alloyed cast iron in physics, tribology and corrosion resistance. This research has significance for the laser surface treatment of various cast irons and steels, which is an increasingly important manufacturing technology in the vehicle friction brake industry.